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Title: Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials

Determining the strength of Li binding to Mo is critical to assessing the survivability of Li as a potential first wall material in fusion reactors. Here, we present the results of a joint experimental and theoretical investigation into how Li desorbs from Mo(110) surfaces, based on what can be deduced from temperature-programmed desorption measurements and density functional theory (DFT). Li desorption peaks measured at temperatures ranging from 711 K (1 monolayer, ML) to 1030 K (0.04 ML), with corresponding desorption onsets from 489 to 878 K, follow a trend similar to predicted Gibbs free energies for Li adsorption. Bader charge analysis of DFT densities reveals that repulsive forces between neighboring positively charged Li atoms increase with coverage and thus reduce the bond strength between Mo and Li, thereby lowering the desorption temperature as the coverage increases. In addition, DFT predicts that Li desorbs at higher temperatures from a surface with vacancies than from a perfect surface, offering an explanation for the anomalously high desorption temperatures for the last Li to desorb from Mo(110). Analysis of simulated local densities of states indicates that the stronger binding to the defective surface is correlated with enhanced interaction between Li and Mo, involving themore » Li 2s electrons and not only the Mo 4d electrons as in the case of the pristine surface, but also the Mo 5s electrons in the case with surface vacancies. We suggest that steps and kinks present on the Mo(110) surface behave similarly and contribute to the high desorption temperatures. These findings imply that roughened Mo surfaces may strengthen Li film adhesion at higher temperatures.« less
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering
  2. Princeton Univ., NJ (United States). Dept. of Chemical and Biological Engineering
  3. Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering, Program in Applied and Computational Mathematics, Andlinger Center for Energy and the Environment
Publication Date:
Grant/Contract Number:
SC0008598; SC0012890
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 120; Journal Issue: 26; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1390515

Chen, Mohan, Roszell, John, Scoullos, Emanuel V., Riplinger, Christoph, Koel, Bruce E., and Carter, Emily A.. Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials. United States: N. p., Web. doi:10.1021/acs.jpcb.6b02092.
Chen, Mohan, Roszell, John, Scoullos, Emanuel V., Riplinger, Christoph, Koel, Bruce E., & Carter, Emily A.. Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials. United States. doi:10.1021/acs.jpcb.6b02092.
Chen, Mohan, Roszell, John, Scoullos, Emanuel V., Riplinger, Christoph, Koel, Bruce E., and Carter, Emily A.. 2016. "Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials". United States. doi:10.1021/acs.jpcb.6b02092. https://www.osti.gov/servlets/purl/1390515.
@article{osti_1390515,
title = {Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials},
author = {Chen, Mohan and Roszell, John and Scoullos, Emanuel V. and Riplinger, Christoph and Koel, Bruce E. and Carter, Emily A.},
abstractNote = {Determining the strength of Li binding to Mo is critical to assessing the survivability of Li as a potential first wall material in fusion reactors. Here, we present the results of a joint experimental and theoretical investigation into how Li desorbs from Mo(110) surfaces, based on what can be deduced from temperature-programmed desorption measurements and density functional theory (DFT). Li desorption peaks measured at temperatures ranging from 711 K (1 monolayer, ML) to 1030 K (0.04 ML), with corresponding desorption onsets from 489 to 878 K, follow a trend similar to predicted Gibbs free energies for Li adsorption. Bader charge analysis of DFT densities reveals that repulsive forces between neighboring positively charged Li atoms increase with coverage and thus reduce the bond strength between Mo and Li, thereby lowering the desorption temperature as the coverage increases. In addition, DFT predicts that Li desorbs at higher temperatures from a surface with vacancies than from a perfect surface, offering an explanation for the anomalously high desorption temperatures for the last Li to desorb from Mo(110). Analysis of simulated local densities of states indicates that the stronger binding to the defective surface is correlated with enhanced interaction between Li and Mo, involving the Li 2s electrons and not only the Mo 4d electrons as in the case of the pristine surface, but also the Mo 5s electrons in the case with surface vacancies. We suggest that steps and kinks present on the Mo(110) surface behave similarly and contribute to the high desorption temperatures. These findings imply that roughened Mo surfaces may strengthen Li film adhesion at higher temperatures.},
doi = {10.1021/acs.jpcb.6b02092},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
number = 26,
volume = 120,
place = {United States},
year = {2016},
month = {3}
}